The tale of two whistleblowers reflects the Democrats’ differing strategies, as well as the whistleblowers’ own approaches.

The intelligence whistleblower brought the complaint to the Intelligence Community Inspector General, who told Congress about the report but didn’t hand it over because of objections from the White House. Rep. Adam Schiff (D-Calif.), chair of the House Intelligence Committee, immediately brought the case to wide attention.

The tax whistleblower, meanwhile, went straight to Congress ― specifically to the House Ways and Means Committee, which had sued the Trump administration for refusing to provide copies of the president’s tax returns in response to a formal request. Democrats say they need Trump’s returns to make sure the IRS properly enforces tax laws against the president.

But Ways and Means Chair Richard Neal (D-Mass.) is far less outspoken than Schiff, and his approach to the tax case has been cautious. He decided to stay focused on the lawsuit, using the whistleblower’s material to bolster that case.

In a brief last month, the committee told the U.S. District Court for the District of Columbia that a “federal employee” had approached them with “evidence of possible misconduct” and “inappropriate efforts” to influence an IRS audit of the president. The document provided no further detail about the whistleblower, but in a footnote, Democrats offered to tell U.S. District Judge Trevor McFadden all about it in private.

A spokesman for the committee said this week that McFadden, a Trump nominee who donated to the Trump 2016 campaign and volunteered for the Trump presidential transition, has so far not asked to hear more about the whistleblower. He denied a Democratic motion to speed up the case.

Neal declined to discuss the whistleblower this week, citing guidance from House lawyers. Other Ways and Means members who said they closely follow the tax returns issue have said they don’t know anything about the person.

“I think that Chairman Neal has appropriately kept that very close since that person’s job could be in serious jeopardy,” Rep. Lloyd Doggett (D-Texas) told HuffPost.

The tax returns issue has dogged Trump since he refused to release his returns during the 2016 campaign ― and now it could wind up as part of an impeachment proceeding. Democrats moved toward impeachment this week largely as a result of information related to the intelligence whistleblower’s complaint, which is still secret.

Ever since Congress caught President Richard Nixon underpaying his taxes in the 1970s, the IRS has followed a policy of automatically auditing the president and vice president every year.

Trump is the first president since Nixon not to voluntarily disclose his tax returns ― which detail income, charitable donations and taxes paid ― to the public. The New York Times has reported that in the past he fraudulently avoided paying taxes.

In a court brief this week, Ways and Means Democrats repeated that they had evidence from a whistleblower, which they said suggested the regular IRS audit “may not be functioning effectively, in part because of the absence of safeguards to protect IRS employees and the audit process from improper influence.”

The White House has declined to comment on the tax matter. Republicans in Congress have said they don’t know anything about it.

In her Tuesday announcement that the House was officially investigating whether to impeach the president, Speaker Nancy Pelosi (D-Calif.) said the oversight committees, which include Ways and Means, would submit evidence to the Judiciary Committee as it drafts articles of impeachment.

Jeff Hauser, director of the Revolving Door Project, an anti-corruption advocacy group, said the overall impeachment case would be stronger if Democrats could show that the Ukrainian shakedown wasn’t an isolated case.

“The House Ways and Means Committee must figure out a way to make the public aware of the serious cause to worry that the IRS might have been corrupted by Trump,” Hauser said.